Mars Pathfinder Science Results

The mosaic of the landscape constructed from the first images revealed
a rocky plain (about 20 percent of which was covered by rocks) that appears
to have been deposited and shaped by catastrophic floods. This was what
we had predicted based on remote-sensing data and the location of the landing
site (19.13 degrees north, 33.22 degrees west), which is downstream from
the mouth of Ares Vallis in the low area known as Chryse Planitia. In Viking
orbiter images, the area appears analogous to the Channeled Scabland in
eastern and central Washington state. This analogy suggests that Ares Vallis
formed when roughly the same volume of water as in the Great Lakes (hundreds
of cubic kilometers) was catastrophically released, carving the observed
channel in a few weeks. The density of impact craters in the region indicates
it formed at an intermediate time in Marss history, somewhere between
1.8 and 3.5 billion years ago. The Pathfinder images support this interpretation.
They show semi-rounded pebbles, cobbles and boulders similar to those deposited
by terrestrial catastrophic floods. Rocks in what we dubbed the Rock Garden
 a collection of rocks to the southwest of the lander, with the names
Shark, Half Dome, and Moe  are inclined and stacked, as if deposited
by rapidly flowing water. Large rocks in the images (0.5 meters or larger)
are flat-topped and often perched, also consistent with deposition by a
flood. The Twin Peaks, a pair of hills on the southwestern horizon, are
streamlined. Viking images suggest that the lander is on the flank of a
broad, gentle ridge trending northeast from Twin Peaks; this ridge may be
a debris tail deposited in the wake of the peaks. Small channels throughout
the scene resemble those in the Channeled Scabland, where drainage in the
last stage of the flood preferentially removed fine-grained materials.

Taking all the results together, scientists have deduced that Mars was
once more Earth-like than previously appreciated. Some crustal materials
on Mars resemble, in silicon content, continental crust on Earth. Moreover,
the rounded pebbles and the possible conglomerate, as well as the abundant
sand- and dust-sized particles, argue for a previously water-rich planet.
The earlier environment seems to have been warmer and wetter, perhaps similar
to that of the early Earth. In contrast, since the time that floods produced
the landing site 1.8 to 3.5 billion years ago, Mars has been a very un-Earth-like
place. The site appears almost unaltered since it was deposited, indicating
very low erosion rates  and therefore no water in relatively recent
times.

The top image is a view to the northeast of the lander and is annotated
to show the variety of rocks in this landing site and what they tell us.
The red arrows point to rounded boulders and rocks, thought to have been
shaped by the forces of water in flood (rough edges knocked off by the
tumbling action of the water). The blue arrows indicate rocks with sharp
edges and points, most probably ejected from nearby impact craters and/or
ancient volcanic activity. The white areas (of which Scooby Doo is one)
are believed to be deposits left behind by evaporating water, or aggregates
of materials fused together by the action of water.

The lower image is the clearest image yet of Yogi (with the Sojourner
rover taking its Alpha Proton X-ray Spectrometer measurement). It clearly
shows the "two-toned" surface of this large rock. The nature
of this color difference is not known, however. It might consist of wind-blown
dust accumulated on the surface (the rock is leaning into the prevailing
wind) or might be evidence of a break from a larger boulder as it was deposited
in the ancient flood that scoured this area.

This false color image of the area surrounding Yogi shows clear evidence
of "scalloped" features in the soil associated with wind-blown
dust. Such evidence indicates clearly the direction of prevailing winds
in this area, and gives further proof of the aeolian nature of erosional
processes on Mars.

October 8, 1997 Press Conference Images - Dr. Matthew P. Golombek

This image close-up of the rock "Moe" was taken from the Sojourner
rover's left front camera on 70 (September 13). Flute-like textures on
the rock, possibly caused by wind abrasion, are clearly visible.

This image of the rock "Half Dome" was taken by the Sojourner
rover's left front camera on Sol 71 (September 14). Pits, linear textures,
and pronounced topography on the rock are clearly visible.

This image pair of the rock "Chimp" was taken by the Sojourner
rover's front cameras on Sol 72 (September 15). Fine-scale texture on Chimp
and other rocks is clearly visible. Wind tails, oriented from lower right
to upper left, are seen next to small pebbles in the foreground. These
were most likely produced by wind action.

This image pair of the rock "Chimp" was taken by the Sojourner
rover's front cameras on Sol 72 (September 15). Fine-scale texture on Chimp
and other rocks is clearly visible. Wind tails, oriented from lower right
to upper left, are seen next to small pebbles in the foreground. These
were most likely produced by wind action.

This color image mosaic shows areas that have recently been traversed by
the Sojourner rover. The large, prominent rocks on the right comprise the
"Rock Garden." The three main rocks making up this assemblage
were all analyzed by Sojourner's Alpha Proton X-ray Spectrometer (APXS).
They are (from left to right) "Shark," "Half Dome,"
and "Moe." Other rocks examined by the APXS include "Wedge"
(wedge-shaped rock in middle foreground), "Stimpy" (in front
of Moe), and "Chimp" (tabular rock in middle-left background)

October 8, 1997 Press Conference Images - Dr. Henry Moore

This Sojourner rover image of the "Cabbage Patch" shows small
rounded objects on the surface that are about 3-4 cm across. Some of these
are within excavations, which are about 0.5 cm wide. Several questions
arise about the pebbles: 1. Why are they rounded? 2. Where did they come
from? 3. What do they mean? Geologists use MULTIPLE WORKING HYPOTHESES
when attempting to explain observations. Some hypotheses that could account
for the pebbles are:

They were rounded during transport by waters of catastrophic floods
and deposited on the Ares Vallis flood plain.

They were rounded by wave action on an ancient Martian beach.

They were rounded during glacial transport.

They are glasses that were produced by melting during impact cratering.
The glass was first ejected from the crater, then molded into spherical
shapes or drops as it traveled through the atmosphere, and finally was
deposited at the sites.

They are spatter from lava flows.

They are nodules brought up from the deep Martian interior by lava
flows or pyroclastic eruptions.

They are concretions formed in sedimentary rocks.

They came from ancient conglomerate rocks. The pebbles were rounded
by water action and subsequently lithified into conglomerate rocks. Later,
the waters of catastrophic floods transported the conglomerates and deposited
them on the Ares Vallis flood plain. The pebbles were then freed from the
rocks by weathering.

A combination of the above.

Pebbles are also seen in lander images, along with cobbles. For example,
in this picture, we see the same pebbles that were visible in the Sojourner
rover image of the "Cabbage Patch" (Figure 1). In addition, a
cobble within the rock "Lamb" (upper left) is apparent. This
indicates that Lamb may be a conglomerate (Lamb is 0.32 m x 0.15 m).

This color composite image from the Pathfinder lander shows the rock "Shark"
at upper right (Shark is about 0.69 m wide, 0.40 m high, and 6.4 m from
the lander). The rock looks like a conglomerate in Sojourner rover images,
but only the large elements of its surface textures can be seen here. This
demonstrates the usefulness of having a robot rover "geologist"
able to examine rocks up close.

This color composite image of the "Rock Garden" shows the rocks
"Shark" and "Half Dome" at upper left and middle, respectively.
Between these two large rocks is a smaller rock ( about 0.20 m wide, 0.10m
high, and 6.33 m from the lander) that was observed close-up with the Sojourner
rover (see Figure 6).

This rover image of "Shark" (upper left center), "Half Dome"
(upper right), and a small rock (right foreground) reveal textures and
structures not visible in lander camera images. These rocks are interpreted
as conglomerates because their surfaces have rounded protrusions up to
several centimeters in size. It is suggested that the protrusions are pebbles
and granules.

This close-up Sojourner rover image of a small rock shows that weathering
has etched-out pebbles to produce sockets. In the image, sunlight is coming
from the upper left. Sockets (with shadows on top) are visible at the lower
left and pebbles (with bright tops and shadowed bases) are seen at the
lower center and lower right. Two pebbles (about 0.5 cm across) are visible
at the lower center.

October 8, 1997 Press Conference Images - Dr. Wes Ward

This image is of so-called wind drifts seen at the Viking 1 landing
site. These are somewhat different from the features seen at the Pathfinder
site in two important ways.

These landforms have no apparent slip- or avalanche-face as do both
terrestrial dunes and the Pathfinder features, and may represent deposits
of sediment falling from the air, as opposed to dune sand, which "hops"
or saltates along the ground;

these features may indicate erosion on one side, because of the layering
and apparent scouring on their right sides. They may, therefore have been
deposited by a wind moving left to right, partly or weakly cemented or
solidified by surface processes at some later time, then eroded by a second
wind (right to left), exposing their internal structure.

This enhanced color image of the Pathfinder landing site shows the eastern
horizon. The elongated, reddish, low contrast region in the distance is
"Roadrunner Flats.".

This is an image from the super-pan sequence. Of importance are some of
the features around the rock nicknamed Barnacle Bill in the left foreground.
The rock shows a "streamlined tail" composed of particles deposited
by wind on the leeward (downwind) side of the rock. Also seen is a "moat"
around the opposite (windward) side of the rock where either erosion (or
non-deposition) of fine sediment has occurred. Mars Pathfinder scientist
believe that the wind blowing over and around rocks like Barnacle Bill
creates an airflow pattern wherein a buffer zone is formed immediately
upwind of the rock and airflow patterns keep sediment from being deposited
directly upwind of Barnacle Bill. On the downwind side, however, the airflow
is complex and a small wake and tapered "dead air zone" form.
Sediment can be deposited within this region and the shape of the formed
deposit corresponds to the airflow patterns that exist behind the rock.
Similar features have been observed at the Viking landing sitess and are
thought to form under high wind conditions during the autumn and winter
seasons in the northern hemisphere. This image mosaic was processed by
the U.S. Geological Survey in support of the NASA/JPL Mars Pathfinder Mars
Mission.

A close-up view of the rock "Moe" in the Rock Garden at the Pathfinder
landing site. Moe is a meter-size boulder that, as seen from Sojourner,
has a relatively smooth yet pitted texture upon close examination. Such
a texture is seen on Earth on rocks that have been abraded by wind in a
process that is analogous to sand blasting. This view of Moe shows two
faces on the rock, one (left side of the rock) facing north-northeast and
the other (right side) facing east. These two faces are thought to have
been pitted and fluted by strong, "sand"-carrying winds from
the northeast.

This pair of images shows a broad view (upper image) and detailed close-up
view (lower image) of the disturbed surface near and on Mermaid Dune. Seen
slightly right of center in the upper image are two diggings by the rovers'
wheel. The uppermost rut is in the surface away from Mermaid and is considered
to be typical of the surface at the landing site. The closer rut represents
the surface at the base of Mermaid on the upwind side. The lower image
is an enlargement of the disturbed Mermaid sediments plus those of the
underlying substrate; that is, the ground upon which the dune lies. Seen
in the close-up are at least two types of sediment, one that seems to be
approximately 1.4 cm thick and forms piles with sides sloping at approximately
35 degrees, and another at least 3 cm deep composed of sediment that has
a characteristic slope of 41 degrees when piled. It is apparent in the
images that there is a size range of sediment present in the rut, sediment
that ranges from a few millimeters in size down to below the resolution
of the camera.

This is an image of the rover Sojourner at the feature called Mermaid Dune
at the landing site. Mermaid is thought to be a low, transverse dune ridge,
with its long (approximately 2 meter-) axis transverse to the wind, which
is thought to come from the lower left of the image and blow toward the
upper right. The rover is facing to the lower left, the "upwind"
direction. The rover's middle wheels are at the crestline of the small
dune, and the rear wheels are on the lee side of the feature. A soil mechanics
experiment was performed to dig into the dune and examine the sediments
exposed.

The rock "Stimpy" is seen in this close-up image taken by the
Sojourner rover's left front camera on Sol 70 (September 13). Detailed
texture on the rock, such as pits and flutes, are clearly visible.

This image was taken by the Sojourner rover in the area behind the "Rock
Garden" at the Pathfinder landing site and gives a view of the Martian
surface not seen from the lander. Of note here are several dune-like ridges
in the foreground. These features are less than a meter high but several
meters wide. They are thought to be created by surface winds blowing right
to left (approximately northeast to southwest). These features are called
dunes, because of their asymmetry, although the rover has not examined
the sediment within them. Such sediment on Earth would be sand-size grains
less than 1 millimeter in diameter.

This is a representation of sediment tails noted at the Mars Pathfinder
landing site. The arrows in the figure represent the inferred downwind
direction, based on our understanding of the deposition of very fine sediment
around surface rocks. The inferred wind direction therefore, is from the
northeast blowing toward the southwest. This wind trend matched that of
light and dark "streaks" of sediment in and around Martian craters
in the region that were seen by the Viking spacecraft. The detailed map
was prepared by Mars Pathfinder scientists from Arizona State University
on a base image created by MPF scientists from the NASA Ames research facility.

Diversity of rover deployment

"Flat Top" and nearby soils

Diversity of rover deployment

Mars color variations

The surface near the rover's egress from the lander
contains bright red drift (#1), dark gray rocks such as Cradle (#3), soil
intermediate in color to the rocks and drift (#2), and dark red soil on
and around the rock Lamb (#4). Globally, Mars is characterized by similar
color variations. The spectra of these sites have been ratioed to the drift
to highlight their differences. The rocks are less red and have less of
a bend in the spectrum at visible wavelengths, indicating less ferric minerals
and a more unweathered composition than drift. The intermediate colored
soils appear intermediate in the spectral properties as well. The dark
red soil at Lamb is darker than drift by about equally as red; the curvature
of sppectrum at visible wavelengths indicates either more ferric minerals
or a larger particle size.

The surface near the rover's egress from the lander
contains mainly bright red drift (#1), dark gray rocks such as Cradle (#3),
soil intermediate in color to the rocks and drift (#2), and dark red soil
on and around the rock Lamb (#4). Globally, Mars is characterized by similar
color variations. The spectra, measured using the full 13- color capability
of IMP, provide evidence for the mineralogy of the unweathered rocks and
highly weathered red soils.

The first color panorama returned by IMP after
Mars Pathfinder's landing included several larger, gray rocks, bright red
dust on a flat- topped rock and the ground between the rocks, and darker
red soil exposed where Pathfinder's landing dislodged a small rock. The
less red color and low reflectance of the rocks is consistent with the
iron minerals found in igneous rocks, whereas the fine, bright drift has
a spectrum indicative of a weathering product. The strength of the bend,
or "kink", in the spectrum is related to the abundance and particle
size of specific crustalline, ferric weathering products. In the false
color image, the blue areas have a weak kink and are relatively unweathered,
whereas the red areas' strong kink indicates an abundance of ferric iron
minerals.

Rocks and soils on the surface are thought to
be composed of minerals similar to those found on earth's surface. One
of the most important tools for recognizing these minerals is the spectrum
of sunlight reflected by them. At the visible and near-infrared light wavelengths
measured by the Imager for Mars Pathfinder (IMP), the most important coloring
materials in the martian surface are iron minerals. There are two broad
classes of iron minerals. Minerals which occur in igneous rocks (such as
pyroxene) have a relatively flat spectrum and they reflect only a small
amount of light; they are said to have a low reflectance. Ferric iron minerals,
which occur as weathering products, reflect longer-wavelength light and
absorb short-wavelength light, hence their very red color. The relative
brightnesses of Martian surface materials in IMP's different wavelength
filter is a powerful tool for recognizing the iron minerals present.

Spectral mapping of site

"Ginger"- highly weathered rock

First look at rock properties

Rover deployed at "Yogi"

The shapes of the spectra of surface
materials can easily be measured from multispectral images. Measures of
surface spectral properties can also be shown as false color overlain on
an image to summarize spectral variations near the lander at a glance.
The top image showns the region southeast of the lander in true color.
In the bottom image of the same region, the strength of the kink in the
spectrum at visible wavelengths (related to the abundance and particle
size of weathered ferric iron minerals) is shown in false color. Blue rocks
are the least weathered, red soils are most weathered, and green soils
and rock faces show an intermediate state of weathering.

The earliest survey of spectral properties
of the rocks and soils surrounding Pathfinder was acquired as a narrow
strip covereing the region just beond the where the rover made its egress
from the lander. The wavelength filters used, all in the binocular camera's
right eye, cover mainly visible wavelengths. These data reveal at least
five kinds of rocks and soil in the immediate vicinity of the lander. All
of the spectra are ratioed to the mean spectrum of bright red drift to
highlight the differences. Different occurrences of drift (pink spectra)
are closely similar. Most of the rocks (black spectra) have a dark gray
color, and are both darker and less red than the drift, suggesting less
weathering. Typical soils (green spectra) are intermeidate in properties
to the rocks and drift. Both these data and subsequent higher resolution
images show that the typical soil consists of a mixture of drift and small
dark gray particles resembling the rock. However two other kinds of materials
are significantly different from the rocks and drift. Pinkish or whitish
pebbles and crusts on some of the rocks (blue spectra) are brighter in
blue light and darker in near-infrared light than is the drift, and they
lack the spectral characteristics closely associated with iron minerals.
Dark red soils in the lee of several rocks are about as red as the drift,
bust consistently darker. The curvature in the spectrum at visible wavelengths
suggests either more ferric iron minerals than in the drift or a larger
particle size.

One of the more unusual rocks at the
site is Ginger, located southeast of the lander. Parts of it have the reddest
color of any material in view, whereas its rounded lobes are gray and relatively
unweathered. These color differences are brought out in the inset, enhaced
at the upper right. In the false color image at the lower right, the shape
of the visible- wavelength spectrum (related to the abundance of weathered
ferric iron minerals) is indicated by the hue of the rocks. Blue indicates
relatively unweathered rocks. Typical soils and drift, which are heavily
weathered, are shown in green and flesh tones. The very red color in the
creases in the rock surface correspond to a crust of ferric minerals. The
origin of the rock is uncertain; the ferric crust may have grown underneath
the rock, or it may cement pebbles together into a conglomerate. Ginger
will be a target of future super- resolution studies to better constrain
its origin.

In this scene showing the rover deployed
at Yogi, the colors have similarly been enhanced to bring out differences.
The same three kinds of rocks are recognized as in the distance. Yogi (red
arrow), one of the large rocks with a weathered coating, exhibits a fresh
face to the northeast, resulting perhaps from eolian scouring or from fracturing
off of pieces to expose a fresher surface. Barnacle Bill and Cradle (blue
arrows) are typical of the unweathered smaller rocks. During its traverse
to Yogi the rover stirred the soil and exposed material from several cm
in depth. During one of the turns to deploy the APXS (inset and white arrow),
the wheels dug particularly deeply and exposed white material. Spectra
of this white material show it is virtually identical to Scooby Doo, and
such white material may underly much of the site.